Up to this time, molybdenum and molybdenum alloys have been deformed by hammer forging or press forging in more than one step.
Hammer forging involves the use of frequent blows to the material much in the same manner as a blacksmith forming a horseshoe with an anvil and hammer. The impact or transfer of force from the dies to the material occurs very rapidly resulting in unknown strain rates on the material. This happens every instance that the rams attempt to come together. It takes numerous blows to achieve the desired amount of deformation or, more particularly, reduction in height of the part. Under normal conditions, this occurs in a five to ten minute time period, but it is a one-step process (no cooling down and reheating, etc.) This method of deforming is very costly and the strain rate cannot be controlled. As a result there is a chance of the resulting deformed parts having defects.
Press forging is a type of deformation which up to this time has required many heating and cooling steps. In press forging, a constantly increasing pressure is applied to the material. The part is squeezed between one hydraulically powered ram and a stationary ram, both of which have dies attached to them. Since the rate of increase (speed at which the rams are brought closer to one another) can be controlled, the strain rate on the material can be specified. The plurality of steps in press forging makes the process time consuming.